Computer support of design activities within precision devices speeds up achieving proper technical solutions, makes documentation to be developed more easily and reduces risk of making errors. Computer simulation of operation of devices being designed plays a significant role in this process. Besides performance characteristics of the device determined this way it also seems to be important to predict analytically other kinds of product characteristics i.e. reliability and availability. A concept of modelling of electrical drive systems for precision devices, verified along the years there is presented in the paper. It seems to be convenient from the point of view of designer. A proposal to utilise simulation results for better prediction of the device reliability is added. and Obsahuje seznam literatury